Current and future munitions energy systems need to be able to provide power for munitions having an ever increasing number of sensors, actuators, and communications requirements. Furthermore, for some munitions, power consumption takes place before, during and after the launch of the munition.
Existing munition energy systems suffer from several problems, including low reliability, limited shelf life, poor gun launch survivability, and high cost. Common causes of low reliability are the need for multiple batteries and their construction. For long shelf life and high reliability, thermal or liquid reserve battery technologies are typically used in which the reactive components of the battery system remain separated until needed. A disadvantage of such systems is primarily the time needed to mix the reactive components and bring the battery output voltage to the desired level. This process is often started using the launch acceleration forces of the munition system and typically takes a set amount of time, up to approximately 30 milliseconds. If power is required during the period of time that the munition is in the launch tube and until the battery system is fully up, another battery system, typically a lithium-based battery system, is often used. Lithium battery technologies, however, are prone to leakage and have much lower shelf lives when compared to thermal or liquid reserve batteries. The second battery system which is added to provide power during the early portions of the launch thus severely degrades the performance of the munition energy system, its shelf life and survivability.
In addition to shelf-life, reliability and survivability, the powering of gun-fired munitions presents additional challenges including, for example, the ability to be stored and operate over wide temperature ranges; acceleration forces ranging from ten to one hundred thousand times the weight of the system; and strict limitations on the volume of space available for housing the energy system.
Moreover, the development of guided munitions and increasing electronic functionality has placed numerous demands on munitions energy systems that did not exist in previous generations of munitions. A significant demand is the requirement to power sensors and actuators, process signals, and communicate much earlier in the flight of smart munitions, sometimes while a munition is inside the gun barrel and during launch.
To overcome the drawbacks of thermal or liquid reserve battery technologies, other battery technologies are being used that allow power to be readily available when needed. The problem with such battery technologies is that these have much lower shelf lives, limited temperature performance and perform poorly in high “G” environments. Older battery technologies often require multiple batteries, have poor shelf life and temperature performance, are large, occupying precious munition volume, have poor acceleration performance, are expensive to produce, and are unreliable.
The issue of volume occupied by the energy system, particularly the batteries, is further exacerbated for gun-fired munitions. Such munitions are subject to very high accelerations during firing with accelerations in the range of 10,000 to 70,000 Gs. In addition, such munitions are commonly subjected to high levels of vibration during transportation and loading. These conditions necessitate the provision of appropriate means to isolate and protect the batteries and their related components (e.g., contacts, wiring, electronics) from damage such as breakage due to plastic deformation, fatigue or other modes of failure or improper operation. Therefore, even more space is required for the housing and protection of the energy systems of gun-fired munitions. As a result, a considerable portion of the available space must be assigned to house the batteries and their related components.
In addition to the aforementioned problems, conventional energy systems for munitions also face problems related to deterioration during long periods of storage (e.g., twenty years), and the high cost of production and assembly of the projectile and the related hardening efforts and testing, among others.
A need therefore exists for munitions energy systems that overcome the aforementioned drawbacks of known systems.